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The Importance of pH Levels in Soil

By: Lacey Russell, PhD | June 21st, 2018


Summer is here! One important task of landscape maintenance is managing your soil pH. The pH of your soil, when managed properly can help you succeed in growing the plants you desire. pH levels measure the amount of hydrogen atoms in the soil and can make valuable nutrients available or unavailable to your beloved trees and plants.

Ranging on a scale of 1 to 14, the pH level measures the acidity or alkalinity of the soil. Acidic soils will have a range of 1 to 6 while alkaline soils will range from 8 to 14, (but we rarely see values above 10). A neutral soil will be very close to 7. Most lawn and garden plants are happy to grow in soils with pH levels around 6.5.

Let me tell you the story of a sadly unproductive vegetable garden where the nutrients, although present in the soil, were not available to the plants because of a problem pH level. After my husband and I bought our house we build a raised garden bed in the backyard to grow vegetables and some cut flowers. We also decided to splurge and spend the money on some high dollar compost sold by the yard. Enriching our soil with compost would provide our plants will a fertile soil that also has great water retention. This would minimize the fertilizer and water inputs to our garden.

In our minds, it would also give us bragging rights as we collected baskets full of ripe vegetables. We filled our garden with the rich black stuff while images of lush healthy plants danced in our heads. Time to plant! We carefully placed each seed and transplant in the perfect spot with labels and sketched a map in our garden journal to identify each unique cultivar we choose to plant.

Weeks went by and we watched our vegetable dreams turn yellow and struggle to survive. We lost several pepper plants and our tomatoes took a long time to start growing. What was wrong? One crucial step we failed to execute before planting our garden was to get a soil test!

Me, the person who has taught soil science at Stephen F. Austin State University a number of times, has worked in a soils testing lab and sat through many Master Gardener lectures that proclaimed, "Get a Soil Test!" should have known better. After sadly watching our vegetables struggle to produce and simply look pitiful, I finally took the time to gather some soil samples and bring them into the lab.

I was so surprised to find that our pH level was sky high! The lab reported it to be 8.8! That explained the stunted growth, the yellowed leaves and the poor vegetable production. Our sad season of slow growth, low production and, wounded egos could have been avoided if only I would have tested the soil before we planted our vegetables and hopes into the very alkaline soil.

To remedy the situation we applied elemental sulfur to lower the pH level and deeply tilled the garden to incorporate more of the native soil with the compost. When you apply elemental sulfur the activity of bacteria do the work to acidify the soil.

Because bacteria do most of their work during warm weather, we are hoping that this winter was mild enough for the pH level to have dropped at least 2 points. I will be doing a soil test here soon. For more information about soil testing contact your local county extension agent or tree health specialist.